London's air pollution levels of nitrogen dioxide exceed EU levels by 50% in some areas. Photograph: Carl De Souza/AFP/Getty Images

Air pollution from traffic and industry is dangerously high in east London, according to tests by local "citizen scientists".

Local environment groups placed 36 diffusion monitoring tubes on structures close to parks, bus stops, busy roads and in residential areas, to measure emissions in more than 30 streets. They were left for four weeks and only four were removed or stolen.

Analysis by a laboratory used by government found that concentrations of the toxic exhaust pipe gas nitrogen dioxide (NO2) exceeded EU levels by over 50% in some areas, and was over the safety limit in 15 out of 32 places tested.

The experiment suggests that official testing of roadside air pollution is limited and insufficient. Many of the tubes measured emissions in streets that are never monitored, and those placed near official monitors mostly recorded levels above those published by government.

Environment groups expect air pollution to deteriorate further in east London if two major infrastructure developments are permitted. City airport has submitted plans which could allow it to add 50,000 more flights a year. Boris Johnson also wants a new Thames road crossing that could massively increase traffic.

"Our sampling showed that in key public locations readings are breaching EU guidelines. We are being asked to believe that the massive expansion of London city airport will have only a negligible impact on air quality. This shows it is simply not the case," said Alan Haughton of Stop City Airport.

"Many busy roads in London are currently way over EU legal limits for NO2, and government does not expect London to meet limits for at least 12 years," said Jenny Bates, a Friends of the Earth pollution campaigner.

"Dangerous levels of air pollution in the capital already shorten lives and cause ill-health. We can't afford to make things worse. Allowing any new road river crossing or London City airport development would be a traffic-generating, pollution-worsening disaster," she said.

The groups called for the mayor and local councils to bring air pollution in London down to EU legal limits as fast as possible.